Laurie Holden
March 31, 1997

Photometric Measurements of Comet Hale-Bopp

Abstract. I have been observing and taking photometric measurements of the comet Hale-Bopp since last November. Photometry is the measurement of the brightness of light (Brandt, Chapman, 1984). By using the CCD (charge coupled device) camera I was able to obtain an image of the comet. Then data reduction on the comet was performed to determine the how bright the comets head is. The formula for determining the magnitude of the comet is: Mag. Comet=Extracted Mag. Object-Extracted Mag. Ref.+2.5log(time object/time ref.)+know mag. Of ref.star. My results show that the comets magnitude has increased since last November. As of March 12, 1997 the magnitude was about 1. Next I applied Morris' law to my data to determine the magnitude of the comet vs. the distance of the comet from the Sun. Morris' law states:observed mag.=absolute mag.+5log (delta)+2.5n log (r). The "n" in the equation determines how rapid the comet changes brightness the closer it gets to the Sun. N=4 is the overall average for comets and my data states that n=8 which means that this is a very volatile comet. This comet is so large and so volatile that we can hypothesize that Hale-Bopp has not made many trips around the Sun and is probably a "virgin" comet.